Extensible, tiltable, counterbalanced lamp bracket



July 9, 1968 A. c. PERBAL 3,391,390

EXTENSIBLE, TILTABLE, COUNTERBALANCED LAMP BRACKET Filed May 19, 1966 2 Sheets-Sheet 1 INVENTOR ALBERT C. PERBAL BY fig ATTORNEY A. C. PERBAL July 9, 1968 EXTENSIBLE, TILTABLE, COUNTERBALANCED LAMP BRACKET 2 Sheets-Sheet 2 Filed May 19, 1966 INVENTOR ALBERT C. PERBAL ATTORNEY United States Patent 3,391,890 EXTENSIBLE, TILTABLE, COUNTERBALANCED LAMP BRACKET Albert C. Perbal, 801 S. Skinker Blvd., St. Louis, Mo. 63130 Filed May 19, 1966, Ser. No. 551,433 11 Claims. (Cl. 248280) ABSTRACT OF THE DISCLOSURE A freely extensible bracket, for electric lamps and the like, projects a mass-balance aft as the bracket head is extended forward of a tilt-permitting support point. Proportion-maintaining mechanism keeps the center of gravity at the support point, regardless how the bracket is extended and tilted. When the bracket head is a lamp, the mass balance may be a transformer in the lamp circuit.

This invention relates to extensible brackets for the support of electric lamps and other articles, and particularly to brackets which are extensible through a broad range of chosen positions and degrees of tilt.

In prior adjustable brackets for electric lamps and the like, such as shown in my US. Patent Nos. 2,200,518, 2,299,251 and 2,665,102, balance in a chosen position within a single plane has been achieved by the use of varying spring forces. The mechanisms employed were so complex as to be likely to possess, inherently, a substantial amount of friction. The bases required for such brackets for lamps were usually large in size, both to balance the lamps and to house auxiliary electrical elements, such as the transformers used in fluorescent lamps. Such spring balance mechanisms usually had to be adjusted as the tilt of the base portion was changed (for example, when used on drawing boards). Spring mechanisms are incapable of balancing out vibratory impulses exerted on the support masses; hence, when such a lamp is mounted on a factory machine, the machines vibrations may cause the lamp to move from the position in which it was set. Such brackets have not heretofore possessed universal tiltability; thus where a lamp head was to be positioned at an angle of tilt or twist, it was necessary to mount it on a separate friction-mount (as shown in my U.S. Patent No. 2,334,436) to permit such tiltable positioning.

The purposes of the present invention are generally to overcome these deficiencies in the prior art. Specifically the present purposes include providing a bracket which projects a mass-balance element rearward as the lamp head or other supported article is extended forward, balancing it precisely regardless how far it is extended. Other purposes are to provide for tilt of the bracket, i.e. of the plane in which it may be extended and retracted, and to render the bracket independent of the slope of the base which supports it. Still other purposes include utilizing such a bracket as part of a unique electric lamp of the type requiring auxiliary elements, such as transformers or batteries, in which the weight and volume of base support and housings are minimized, and in which the lamp head may be maintained balanced at a tilt angle by the same balance means which maintains the position of the lamp head.

For balancing and tilting in more than one plane, the extent of angular movement of a conventional ball joint has not proved to be entirely adequate. Hence an additional purpose of the present invention is to provide suitable support means including a support point characterized by a sufficient degree of three-axis freedom to achieve the other purposes, and yet which can be readily controlled by the user.

3,391,890 Patented July 9, 1968 Generally summarizing the present invention, I provide a support bracket of extensible, proportion maintaining geometry, to project a mass-balancing element aft as the lamp head or other supported article is extended forwardly. The center of gravity of the masses so mounted coincides with or is close to the support point; and the proportion-maintaining mechanism preserves the center of gravity location throughout the range of extended positioning and regardless how tilted. A key element of this geometry is a link, which in the mid-range of its movement slopes up and aft. To give this link three-axis freedom, in the preferred embodiment I mount it on a swiveled fitting to a horizontal balancing hinge, which in turn is supported on the top extension of a pivoted base. This top extension slopes from the support point forward and down and then aft in a bend, back to the pivot axis of the base. When the bracket is folded, the mass-balancing element fits neatly into the bend. Applied to an electric lamp having in circuit heavy-weight auxiliaries such as transformers or batteries, I utilize these as the weighty mass-balance elements, and house them on the aft-projecting part of the mechanism. Since the center of gravity of the balanced elements coincides closely with the support point regardless how the lamp is extended or tilted, the base is both small in size and light in weight.

In the accompanying drawings:

FIG. 1 is a side elevation of a counter-balanced electric lamp embodying the present invention. Its fully-folded position is shown in phantom lines. The dashed lines show the lamps geometry in fully extended position.

FIG. 2 is a front elevation of the lamp of FIG. 1, the phantom lines showing same in laterally tilted position.

FIG. 3 is a side elevation similar to FIG. 1 showing the lamp head raised.

FIG. 4 is a top plan view showing the lamp tilted laterally from the FIG. 3 position, which is indicated in phantom lines.

FIG. 5 is an enlarged fragmentary view of the support point means, taken along lines 55 of FIG. 4.

FIG. 6 is a top view of those portions shown in FIG. 5, partially exploded and broken away.

FIG. 7 is a view similar to FIG. 6 of an alternate support point means, the portions at the right side thereof being shown rotated into the plane of the drawing.

The principal portions of the embodiment of the invention shown in the drawings are generally designated as the base 10, a pivoted bend 20, support point means 30, an extensible bracket of proportion-maintaining geometry 50, a lamp head supported thereby 70 for forward extension from the support point, and the mass balance housing 60 containing the weighty electrical element which are projected rearwardly as the lamp head is extended forwardly. As later discussed, the center of gravity of all masses balanced on the support point 30 remains in the same place regardless how the lamp head may be extended and tilted. The base 10 thus may be very small. Shown is a disc-like base plate 12 supporting at its center a vertical hollow tube stem 13. A simple bearing 14 inserted into the upper end of the stem 13 provides a vertical pivot axis a-a. Mounted in the top thereof by a pin 21 is the pivoted bend 20 at whose upper end is the support point means 30, supported by it vertically above and in alignment with the pivot axis aa. The pivoting bend is preferably constructed as a curved rigid arm 22 bent from flat steel strip, thus to serve as pivoting support structure. The top end of the arm 22 has locking notches 23, shown in FIGS. 6 and 7, in both of its edges. Its forward and downward slope from the support point 30 is utilized as hereinafter mentioned.

The support point means 30 is constructed, not as a simple lateral hinge to give freedom of movement in a vertical plane only, nor as a conventional three-degree-offreedom ball or universal joint. Instead it is characterized by two degrees of freedom, to which is added in effect the freedom of movement provided about the vertical pivot axis a-a. Referring to the enlarged fragmentary views in FIGS. and 6, the notches 23 of the arm 22 hold molded support point halves 31, by interlocking of the projections 32 into their molded strap accepting cavity 33. Aligned lateral 'bore portions 34 receive a squareheaded machine screw 35 and nut 36, which hold the parts in assembly and also provides an adjustable amount of friction to opposed cylindrical sockets 37, Whose inwardpresented faces 38 define a clevis and bear against the outer annular faces 39 of a pair of trunnion mounts generally designated 4% having inwardly-presented semicylindrical bushing portions 41 which define a swiveling axis cc. The trunnion mounts 46 are received within the sockets 37. Pressure by the end faces 38 against the outer trunnion mount faces 39 so holds the bushing .portions 41 together to provide in effect a cylindrical bushing about the swiveling axis cc, perpendicular to the lateral balancing axis b-b, as defined by the cylindrical sockets 37.

Held on the axis c-c by the bushing portions 41 is the headed swiveling rod portion 51 of a mechanical link 52 for the proportion-maintaining mechanism of this invention. Due to the upward and aft slope of the upper portion of the arm 22, the assembly consisting of the link 52 and the trunnion mounts are movable in the clevis defined by the inward-presented faces 38, through a large useful angle d shown in FIG. 5, which angle may approach 180. All or most of the useful range of the angle d, through which the swiveling axis cc may move, will be normally out of coincidence with the vertical pivot axis a-a. As long as they are out of coincidence, the link will have in effect three degrees of angular freedom. Contrary to general impression, it is not necessary that all the axes be perpendicular to each other. FIG. 2 shows angular tilt out of the vertical plane vv about the swiveling axis cc when it is nearly horizontal as in FIG. 1. However when tilted downward as in FIG. 3, there is a corresponding freedom of angular tilt, as shown in FIG. 4, hereafter referred to.

The alternate embodiment of FIG. 7 shows certain identical portions which are similarly numbered, whose description is not repeated, and certain functionally-simi lar portions correspondingly numbered with the added designation prime For clarity, the molded support point halves 31', together with the upper end of the arm 22 of the pivoted bend 20 are shown in FIG. 7 rotated into the plane of the drawing. The support point halves 31' have inwardly-presented clevis end faces 38 which, when the parts are assembled by the screw 35 and nut 36, have a spacing substantially equal to the diameter of the rounded neck portion 75 on the modified link generally designated 52'. This neck portion 75 is cylin- V drical about the link swiveling axis c-c. Onto the neck portion 75 is formed a larger-diameter spherical head generally 76; it is clamped between partial-spherical recesses 77 formed in the end faces 38'. The spacing of the recesses 77 within the faces 38' leaves fiat face portions which fit closely against the cylindrical neck 75; hence the link 52' cannot be rotated about an axis through the ball 76 perpendicular to the plane of the drawing FIG. 7. Thus the ball-and-socket joint, provided by the ball head 76 and the partial-spherical recesses 77, does not permit three degrees of freedom, but only two. As with the embodiment of FIG. 6, these two degrees of freedom are adjustably controlled by tightening the nut 36. The third degree of freedom is provided by rotation of the pivoted bend 20 about the pin 21. Axis bb is perpendicular to the end faces 38.

The link 52 extends along a line designated ff, hereinafter referred to as the line of the link, from the support point at the intersection of the swiveling axis cc with the lateral balancing axis b-b. The line ff does not conform with the swiveling axis cc, but is at a substantial angle e thereto which may be approximately 45 as shown in FIG. 6. This serves to set the swiveling axis nearly horizontal when the bracket is adjusted to the FIG. 1 position, and keeps it out of coincidence with the vertical pivot axis a-a throughout the broad range of useful settings within the angle d.

The effective length of the link 52 is its length from said intersection to a fulcrum g having a transverse fulcrum pin 53. Generally above the line of the link ff as shown in FIGS. 3, 6 and 7 (or forwardly as shown in FIG. 1), the link 52 has an enlarged clevis boss 54 in which a parallelism-maintaining rod '55 is pivotally secured by a pivot pin 56.

Parallelism is maintained by the jointed geometry in a plane which, when the bracket is untilted as in FIGS. 1, 2 and 3, coincides with the vertical plane vv. The bracket may be rotated out of the vertical plane vv to any selected angle within the large range of angular tilt zz shown in FIG. 2.

If the jointed geometry be first arranged in the plane vv with the lamp head raised in the position shown in FIG. 3, and then tilted out of the plane vv, the resulting configuration will be as shown in the 'plan view FIG. 4. Prior to such out-of-plane tilting, the swiveling axis cc would be inclined approximately 45 below horizontal as shown in FIG. 3, and the pivoted bend 20 would project forward toward the lamp head 70 as shown in the dashed lines of FIG. 4. On tilting within the range zz through an angle of 90 as shown in solid lines in the plan view FIG. 4, the entire link 52 including its swiveling axis c-c is brought from its inclined FIG. 3 position into a horizontal plane. To permit and adjust for this change in position of the swiveling axis cc, the lateral balancing axis bb assumes the angular position shown in FIG. 4, by causing the pivoting bend 20 to rotate about the axis a-a out of the vertical plane vv through an angle designated h, shown as approximately 45.

Onto the fulcrum pin 53 is pivotally mounted the clevis fitting part 57 molded to project from the under side of an aft lever portion 58. The aft lever portion 58 has at its forward end an integral tube-receiving socket 59 from which it extends aft to an enlarged mass balance housing portion 60, formed curvingly to fit within the bend 20 as shown in phantom lines in FIG. 1.

The tube-receiving socket 59 holds a tubular portion 61 which extends generally forward when the lamp head 70 is extended forward of the base 10 as shown in solid lines in FIG. 1. The normally forward end of the tubular lever portion 61 is received within an aft molded socket part 62 of a hinge joint fitting generally designated 63 and having a hinge pivot axis i parallel to the fulcrum pin 53. From the pivot axis i, and supported in the forward socket part 64 of the hinge joint fitting 63, there extends a tubular arm '65 which (in the FIG. 1 solid line position) projects normally forwardly to a forward attachment means 66 on which the article to be supported (here the lamp head 70) is adjustably mounted.

Mounted to project along the under side of the forward socket part 64 is a forward clevis 67, having a pivot pin 68 connecting the forward end of the parallelism-maintaining rod 55. Since the pivot pins 68 and 5 6 have axes parallel to each other and to the fulcrum pin 53 and the hinge axis 1', and since the spacing of the forward fulcrum pin 68 from the hinge axis i corresponds substantially with the spacing of the aft pivot pin 56 from the fulcrum g, the rod 55 together with its end fittings to the link 52 and forward socket part 64 serves as parallelism-maintaining means.

A center of gravity designated m is found, accurately or approximately, for those masses which the mechanism will project forward as the lamp head 70 is extended forward; these include the arm 65 and its end connections and the supported lamp 70 or the other article attached thereto. The length of the rod 55 is fixed so that the center of gravity m will be supported along a line j-j extending from the hinge axis i and parallel to the line of the link f-f. The rod 55 preserves this parallelism regardless whether the lamp head 70 be in the vertical plane v-v in a usual position such as shown in full lines in FIG. 1, or in the folded position shown in phantom lines, or in the fully extended position shown by the triangular outline. Such parallelism is also maintained regardless of extent of rotation about the lateral balancing axis bb, as when the lamp head 70 is tilted up to the FIG. 3 position; and regardless of tilt through an angle z-z out of the vertical plane vv, such as in tilting from the FIG. 3 position to the FIG. 4 position.

A weighty mass balancing element (which may be the electrical transformer 80 hereinafter referred to) and any supplementary balancing mass which may be required, is afiixed within the mass balance housing portion 60, and so positioned therein as to establish an aft center of gravity 11 for the masses which project rearwardly as the lamp head 70 is extended forwardly. Generally these masses include the tubular lever portion 61 and the molded aft lever portion 58, its mass balance housing portion 60, the mass balancing transformer 80 and any other mass balancing elements. Such center of gravity n is positioned at the intersection of a straight line x-x, which extends from the forward center of gravity m through the support point 30, with a line yy extending from the hinge axis 2' through the fulcrum pin 53. The ratio of the weight acting at the aft center of gravity n to those at the forward center of gravity 111 must be inversely proportional to the ratio of their distances from the support point 30, taken along the line x-x.

This achieves perfect balance, regardless whether the jointed members are moved to the fully folded position shown in phantom lines, in which the forward center of gravity is designated m and the aft center of gravity is designated 11; or into the fully extended position in which said centers of gravity are designated m, n respectively. This is for the reason that with parallelism maintained between the line of the link f-] and the line 'j, the rear center of gravity in (or n or n") will be the apex of similar triangles; extending the supported article forward with reference to the support point will so tilt the always-parallel lines J- and j as to project the center of gravity n rearwardly, maintaining their linearity along line x-x through the support point 39 and the precise inverse proportionality of their distances from the support point 30. (Stated somewhat differently, regardless of the extension, rotation or tilt, the combined centers of gravity of all masses supported on the support point 30 will always be precisely at said support point.)

By reason of such maintained linearity and proportionality, an important new result is achieved. Considering tilting out of the plane v-v, as shown in FIG. 2: since m and it always lie along a straight line xx through the support point 36, the balance of the lamp is in no way disturbed by rotation around this line.

This discovery makes possible the use of a small light weight base 10. The bracket is thus readily manipulated either by grasping the lamp head 70 (or other supported article) or the mass balance housing portion 60, or any other movable part. Joint friction is therefore not necessary for balance. However, some joint friction may be introduced to prevent extremely small forces, such as inadvertent touching, from causing the lamp to swing cut of chosen position. The screw is a convenient means for introducing such friction, as tightening it applies pressure to induce such friction through the trunnion mounts 49 about both the lateral balancing axis b-b and the swiveling axis cc. With some light degree of friction being a practical necessity, the use of such friction also permits less rigorous accuracy in locating the forward center of gravity in and the aft center of gravity n linearly at inversely proportionate distances from the support point 30.

When the bracket mechanism is moved to fully closed upright position shown in phantom lines in FIG. 1, the line jj will become nearly vertical, and the line of the link ff will tilt upward parallel thereto. This raises the mass balance housing portion 69 to set it within the gap provided by the pivoting bend 20. A dimensional requirement to achieve this fit is, that the spacing of the enlarged portion of the mass balance housing 60 from the fulcrum g is slightly greater than the length of the link measured from the lateral balancing axis b-b to the fulcrum g.

An exemplary embodiment of the bracket so described is its utilization as part of the counterbalanced electric lamp illustrated in FIGS. 1-4, wherein a weighty electrical element such as a transformer 80 is housed in the housing portion 60 and is wired in circuit with the lamp head 70. Thus, the mass of the transformer 80 aids in counterbalancing the relatively lighter weight of the lamp head 7%. In ifliS embodiment, 110 volt current flows through the external lamp cord 81 leading through the housing 69, to the transformer 80, from it, lower voltage current flows through the connectors 82 which extend from the housing 69 through the tubular lever portion 61 and hinge joint fitting 63 and the tubular arm 65 to connect to the lamp head 70. Extending the lamp head forward projects the transformer and housing 60 rearward; hence it is convenient that the cord 81 need not extend through the support point 30 though the pivoting bend 2% or base 10.

In other types of lamps, associated weighty electrical elements suitable for the lamps purpose may be substituted for the transformer 88; for example batteries, capacitors, etc. Thus the present invention may be put to many uses, such as light-weight portable lamps, heavy studio lighting equipment, therapeutic lamps, and lamps mounted upon factory machines. It is also excellent for readily adjustable microphone brackets and kindred uses. Since only the lever 59 and arm 65 are wired, it is easy to substitute base structure appropriate for any use.

The present extensible counterbalanced bracket construction is of particular value when used on vibrating machinery. Heretofore extensible machine-mounted lamps have required much joint friction to hold them in fixed position. Spring-balanced lamps are not well suited for such use, because the vibratory or periodic accelerations applied to the lamp heads cannot be balanced out by a spring force, which does not depend upon mass and inertia.

With the present invention, however, periodic accelerations applied to each element of the balanced masses hold the remainder in balance, and do not therefore cause the lamp to change its geometry. If the balanced masses be thought of as being divided between the forward masses at the center of gravity in and at the aft masses of the center of gravity n, the vibrations transmitted to them through the support point means 39 are balanced by proportionate reactions at each. Thus only a small frictional force applied through the screw 35 is necessary to preserve the jointed geometry at any position of extension, rotation and tilt.

Variations in the number and type of elements making up the jointed geometry and the parallelism-maintaining means, and other modifications in utilization of the present bracket structure, may be readily devised. Accordingly the present invention is not to be construed narrowly, but rather as fully co-extensive with the claims hereof.

I claim:

1. An adjustable bracket adapted to support an article in balance throughout a range of positions and angles,

comprising base means to establish the position of a support point, an extensible bracket mechanism balancedly supported thereon and having a forward means to attach such an article supportingly, and including a link having a supported end and fulcrum means spaced from said supported end,

a lever pivotedly mounted onto the fulcrum means and extending forward therefrom to a hinge joint, an arm mounted to said hinge joint and extending therefrom to such forward means to attach such an article,

means extending between the link and the arm to maintain parallelism between a first line from the supported end of the link to its fulcrum means and a second line from the hinge to substantially the center of gravity of masses forward of the support point including the arm and such article attached thereto, and

means to apply to said lever a balancing force aft of the support point whereby to maintain the mechanism balanced at said support point regardless of its extension, characterized in having means to support said supported end of the link with three degrees of freedom of angular movement at said support point, and further characterized in that said means to maintain parallelism is ofiset spacedly from the support point,

whereby said spaced offset permits the extensible mechanism a wide range of arcuate movement including lateral tilting about said support point.

2. An adjustable bracket as defined in claim 1, wherein said means to apply a balancing force comprises a portion of said lever extending aft from the fulcrum and a weighty mass-balancing element thereon,

the mass and position of said element being such that a straight line from said center of gravity of masses forward of the support point and extending aft therethrough will substantially intersect the center of gravity of the mass-balancing element and the lever,

regardless of the extension of the bracket mechanism,

whereby lateral tilting will not disturb the balance of the mechanism at the support point.

3. An adjustable bracket as defined in claim 1, wherein the means to maintain parallelism includes a rod mounted between the link, at a point spacedly offset from the support point, and the arm at a point spacedly offset from the hinge point.

4. An adjustable bracket as defined in claim 1, wherein said means to support the end of the link with three degrees of freedom includes means defining a vertical pivoting axis and means defining an axis for lateral tilting, extending from the support point angularly out of coincidence with said first line to the fulcrum means and below said line when said extensible bracket is at the mid-point of its range of lateral tilt about such axis,

whereby said lateral tilting axis remains out of coincidencc with the vertical pivoting axis when the link is so tilted that said first line is vertical.

5. An adjustable bracket as defined in claim 2, wherein the said means to establish the position of the support points serves as means to provide the degree of freedom about a vertical axis, and includes a base and a member pivoting vertically therein and having a bend away from such vertical axis,

whereby to provide a space along said axis to accommodate the mass-balancing element when the fulcrum means above the said supported end of the link.

6. An adjustable bracket adapted to support an article in balance throughout a range of bracket positions and angles, comprising base means to establish the position of a support point,

an extensible bracket mechanism balancedly supported thereon and extensible in a plane,

said extensible mechanism including a forward attachment means for supporting such an article and being of a type having a point of balance, for said extensible mechanism and such attached article, and interconnecting means to maintain said point of balance at the support point regardless of the extension of said mechanism, in combination with means to support said extensible mechanism with three degrees of freedom of angular movement about said support point,

said means comprising means, operable between the base means and the support point, to establish a first axis of angular move ment through the support point,

means, rotatable on said first axis, to establish a second axis of angular movement substantially perpendicular thereto and intersecting same at said support point, and

means, operable between the extensible mechanism and the support point, to establish a third axis of angular movement through said intersection substantially perpendicular to said second axis and, by rotation thereabout, variable in its angular relation to said first axis,

whereby desired arcuate movement of the extensible bracket about any axis through the support point not coincident with any one of said three axes is accommodated by relative rotation of said means which establish said three axes.

7. An adjustable bracket as defined in claim 6, wherein the means to establish said second axis includes a trunnion-mounted bushing, and

the means to establish said third axis includes a rod portion swivel-mounted in said bushing.

8. An adjustable bracket as defined in claim 6, wherein said means to establish said second and third axes includes a ball and socket joint having means to confine relative movement to movements about said second and third axes.

9. An adjustable bracket as defined in claim 6, wherein said third axis lies in the plane in which said bracket mechanism is extensible,

whereby lateral tilting of said plane of extension may be efiected about said third axis through angles greater than to each side of center.

10. An adjustable bracket as defined in claim 9, wherein the member of the extensible mechanism by which it is supported at the support point is a link having a useful range of angular movement in said plane about said second axis as the mechanism is extended, and

its said range of movement has a mid-point at which the angle made by the third axis with the first axis is substantial,

whereby the third axis is maintained out of coincidence with the first axis through a substantial part of said useful range of movement thereby to maintain unimpaired such relative rotation accommodating arcuate movements not coincident with any axis.

11. An adjustable support bracket as defined in claim wherein the said first axis is substantially vertical and the said second axis is substantially horizontal and lateral with respect to the extensible bracket mechanism, and wherein at the said mid-point of useful range of movement about the second axis, the third axis is substantially fore and aft.

References Cited UNITED STATES PATENTS 2,031,097 2/1936 Bucky 248123 2,548,476 4/ 1951 Horstmann 248281 2,763,500 9/1956 Turner 248-288 X 3,000,606 9/1961 Stormetal 248280 X 3,219,303 11/1965 Stryker 248-280 ROY D. FRAZIER, Primary Examiner. R. P. SEITTER, Assistant Examiner. 

